Thermostatic detector



Sept. 4, 1934. e. H. L. cs. BO RY THERMOSTATIC DETECTOR Filed May 12, 1932 INVENTOR 650F625 H l. 6! 50"?) ATT RNEY- Patented Sept. 4, 1934 1,972,257 THERMOSTATIC DETECTOR Georges Henri Louis Gaston Bory, Paris, France Application May 12, 1932, Serial No. 610,764 In France April 5, 1928 9 Claims. (01. 200-137 This application is a continuation in part of my prior application Serial No. 351,030, filed March 20, 1929.

This invention relates to thermostatic devices,

and more particularly to such devices designed to give an alarm in the event of an abnormal or dangerous rise in the temperature of the outer atmosphere surrounding the device. The function of the device is dependent upon the disturbances of the thermic equilibrium normally I obtained between the thermostatic elements thereof and said atmosphere.

An object of the invention is the provision of .a thermostatic device which is extremely sensitive to comparatively slight, but rapidly increasing, temperature changes of the. surrounding atmosphere.

Another object is the provision of a. heat detector, which although sensitive to slight variations in increased temperatures, is designed to function reliably and accurately, thus assuring positive operation at all times but without the possibility of giving false alarms.

Other objects of the invention having to do with detail of design will manifest themselves upon reading the following specification.

The invention is illustrated in the accompanying drawing, in which: I

Figs. 1 and 2 are longitudinal sectional views of a thermostatic device embodying my invention;

Fig. 3 is a longitudinal elevation, partly broken away, of the device shown in Fig. 2;

Fig. 4 is a longitudinal cross-section of a modifled form of the device shown in Fig. 2;

Fig. 5 is a transverse cross-section of Fig. 4 taken on the line II thereof;

Fig. 6 is a perspective view, with a protective cap partly removed, of a detector mounted upon a supporting base;

Fig. 7 is a longitudinal sectional view of Fig. 6; and

Fig. 8 is an enlarged detail view of the switch members for controlling an electric circuit.

Throughout'the several figures similar parts are indicated by like reference characters.

The invention is somewhat conventionally rep resented by Fig. 1 of the drawing. The form of thermostatic switch shown in Fig. 1 comprises a casing 1,'square in cross-section, which may be formed of two angle bars suitably secured together. Stretched longitudinal of the casing 1 is a wire 2 having one of its ends welded to the casing and the other end held by means of an 55 adjustable screw 3 which allows tensioning of the wire. At the center of the casing 1 is mounted an S-shaped leaf spring l terminating with an incurved end 5 through which the wire 2 passes so as to be prevented from slipping away from the spring. An adjustable screw 6, passing 0 through the casing inside a bushing or sleeve 7 of insulating material, has its end in contact with the spring 4 and closes an electric alarm circuit (not shown) containing a battery, the screw 6 and the body of the device.

Lateral apertures are provided longitudinally of the casing 1, the functioning of which will be more fully described hereinafter. Generally speaking, however, the purpose of these apertures is to afford ventilation to the casing in such a manner as to normally establish thermic equilib rium between the thermostatic elements within the casing and the outer surrounding atmosphere. Since the functioning of my device is dependent upon disturbing this normal equilibrium, it is necessary for the casing 1 and the wire 2 to be of material having different coefficients of expansion andalso having different thermic capacities. I have found that by using brass for the casing and'either silver or German silver for the wire, these requirements are met satisfactorily.

The shape of the casing and the disposition of the openings have been found to have a great influence for the efiiciency of the device. When a fire breaks out, the detector receives at first alter- 8 nately hot and colder waves, until the general temperature increases and the colder waves gradually subside. The shield acts as a trap from heat waves and also somewhat protects the wire from the colder waves. Therefore, in order to obtain a gradual heating of the wire, and retain and concentrate such heating upon the Wire, a shield is provided in the axis of which the wire is placed. The preferred form of the device is shown in which the shield is of tubular shape and of circular section. Another form of the device is when the section is oval or U-shaped. However, such device functions well only when the total area of the openings which are under the horizontal plane passing by the wire is decidedly greater than the area of the openings above such a plane.

The more commercial form of the invention is shown in Figs. 2 to 8, particularly Figs. 6 and 7. In this form the casing l is of tubing, and is provided with end covers or caps 9 and 10. The cap 10 is provided with a cut-away portion toaccommodate the mounting of the adjustable screw 6 and is preferably removable, The leaf spring 4 may have one of its ends welded directly to the casing l, as illustrated in Figs. 2 to 5, or it may secured to a mounting 11 carried by the cassecured to the free end of the spring 4, and the other end said wire is attached to the adjlntg able screw 3 mounted axially in the opposite end of the casing. By this construction the wire 2 may be so tensioned as to normally coincide with the longitudinal axis of the casing 1.

A ilbre washer 13, having an opening in the center thereof, is inserted transversely of the casing 1 and positioned adjacent to the point of contact between the spring 4 and the screw 6. The washer, acting as a baflle, separates the contact members 4 and 6 from the outside atmosphere and protects them against the dust. The cap and the washer 13 also provide protection from tampering by unauthorized persons.

kithough the tension of the leaf spring 4 is in the direction away from the screw 8, the normal U make contact with the tree or movable end of the spring positioned in substantial axial ali nment of the casing. This adjustment is secured by placing the proper amount of tension upon the wire 2 by means oi the adjustable screw 3 and by also regulating the position of the adjustable screw 6. It is obvious a slight release of the tension onthe wire is translated to the spring in a greatly amplified form because the end thereof is permitted to move substantiallyperpendicular to the axis of the casing, as clearly illustrated by Fig. 8. This arrangement insures a positive rupture of the circuit completed through the spring 4 and the screw 6 by a comparatively small elonsation of the wire.

in the modification illustrated in Figs. 2 to 'i it will be noted that the lateral apertures 8 are of inherent sizes and arranged in sets oppositely disposed. the arrangement with respect to the siseof the apertures being such that when the detector is placed in service the larger apertures are presented to the natural flow of air currents. This sheets the ventilation of the casing and the concentration of heat waves along the longitudinal axis, thereby increasing the sensitivity of the device. This concentration of heat waves is produced by the fact that the influx thereof through the large apertures is greater than the emu: through the smaller apertures, and where the casing 1 is tubular in shape, the deflectionpf the heat waves is augmented by the contour of the deflecting portion of the casing. The concentration of the heat waves will be greatest along the longitudinal axis of the detector and it is because of this that I prefer to mount the wire 2 loss to substantially coincide therewith.

In the form of construction shown in Figs. 6 and I, the casing 1 is provided with a supportin; base 14 but electrically insulated therefrom by suitable insulating material 15. This mount- .ing may be eil'ected by providing the caps 9 and 10 with extended portions16 and 17 respectively, terminating in bent over edges 18. The edges 18 ct cap 9 have. holes through which extend suitable screws for fastening the cap to the base 14. The cap 10 may be removably mounted by providing plate members 19 adaptedto form a race for the ilanged or turned over edges 18 o! the cap. said plate member in turn being screwed to the base 14. The friction of these interlocking parts h suillcient to maintain the cap 10 in any desired position, thus making the contact members protected thereby readily accessible. The base 14 is provided with holes 21 by means 1 of which the detector may be secured to t e 09. 1-

adiustment of these members is suchthat they ing of a room or the like. When the detector is mountedthe casing 1 has itslongitudinal axis normal t the hatural flow of air currents caused by atmozpheric conditions, and any sudden change oi temperature will immediately disturb the thermic equilibrium of the thermostatic parts of the detector. As pointed out above, this change of temperature is accentuated by the air currents being deflected and/or concentrated upon the wire 2; resulting in a slackening thereofyandconsequent rupture of contact between the spring 4 and the screw 6. The wire'2 is adapted to expand more rapidly than the casing 1 because of not only their difference in the rates of expansion, but also because of their difference in thermic capacities. This delays the setting in thermic equilibrium of the casing with refer-, ence to the surrounding atmosphere. q

The operation of the detector should be clearly understood from the foregoing but it may be briefly described asfollows. At the time of installing the detector inan alarm system, proper adjustments of the contact members 4 and 6 are made, which includes placing suflicient tension upon the wire 2 as to normally maintain these members in contact. In the event there is likely to be substantial vibration of the ceiling from which the detector is mounted, it may be suspended therefrom by means of dampers, such as coil springs 22. These springs may be attached to suitable brackets 23, fastened to the ceiling and screws 24 carried by the casing 1. The impcrtant thing about the installation of the detector is that the larger apertures in the casing 1 are presented to the air currents naturally arising in the room or in enclosure in which the detector is located; also that the casing '1 has its longitudinal axis mounted normally to said currents. Where there is little, if any, vibration of the ceiling, the dampers 22 may be omitted and the detector fastened directly to the ceiling. When the thermic equilibrium between the thermostatic, elements and the outer atmosphere is again restored, the wire 2 will contract, thus automatically again making contact between the spring 4 and the screw 6.

Thealarm circuit controlled by the detector may be completed through the casing 1, the spring 4 and the screw 6. I1 preferred, this circult couldbe established through the screw 6, the contact formed thereby with the spring 4, and suitable connection made with the adjusting screw 3, which circuit arrangement would include the wire 2 as part thereof.

From the foregoing description it is obvious that the invention is susceptible to a number of modifications and all such modifications are contemplated as come within the scope of the appended claims.

What is claimed is:

l. A thermostatic switch comprising a casing, a wire stretched longitudinally of said casing, said wire being adapted to expand rapidly under the action of heat and having a high coeflicient of expansion, said casing having a lesser coeflicient of expansion and being provided with ventilation for the admission of heat waves, said ventilation being eiiected by means of apertures provided in said casing in opposite sets of' which the area is of distinct predetermined values.

2. A thermostatic switch comprising a casing having apertures of diiierent sizes arranged in sets, the set of larger apertures being arranged oppositely the set of smaller apertures, whereby ventilation through the tube is provided but the influx of heat waves is greater than the eliiux so that a concentration of the waves is effected within the tube when mountedhorizontally with respect to its longitudinal axis.

3. A thermostatic switch comprising a casing, a wire stretched longitudinally of said casing, a substantially S-shaped leaf spring the ends of which are connected respectively with the wire and the casing, the end of said spring which tact inside the casing and means for adjusting the position of the contact for allowing the spring to contact with it when it moves laterally with reference to the normal position of the wire.

4. A thermostatic switch comprising a casing, a metal spring having one of its ends secured to said casing and the other end normally in axial alignment therewith, a wire adapted to expand rapidly under the action of heat and having a high coefficient of expansion, one end of said wire being connected to the free end of said spring and the other to a tensioning device carried by said casing, a contact member cooperating with the spring and carried by said casing but electrically insulated therefrom, the design of said spring being such that a slight release of the tension on the wire is translated to the spring in greatly amplified form, and means for concentrating heat waves upon said wire, whereby the normal thermic equilibrium between said casing and wire is distributed thus permitting lateral movement of said spring.

5. A thermostatic switch comprising a casing, a wire stretched longitudinally of said casing, a substantially S-shaped leaf spring the ends 0! which are connected respectively with the wire and the casing, the end of said spring which is connected with the wire being adapted when the latter expands and slackens to move laterally with reference to the normal position of the wire, an adjustable contact cooperating with the spring, an insulating part securing the contact inside the casing, means for adjusting the position of the contact to allow the spring ,to-

normally engage therewith, means for concentrating heat waves upon the wire, said means including apertures so designed and arranged that an influx of heat waves is greater than the efiiux thereof.

8. A thermostatic switch comprising a metallic sheath, 9. metal spring having one of its ends secured to said sheath, a wire adapted to expand rapidly under the action of heat and having a high coefllcient of expansion, one end of said wire being connected to the free end of said spring and the other to means for adjusting the tension of the wire, said tensioning means being adjusted so that the free end of said spring is normally in engagement with a contact member carried by said sheath but electrically insulated therefrom the design of said spring being such that a slight elongation of the wire permits the end attached thereto to move substantially laterally with reference to the normal position of the wire, whereby a positive rupture of a circuit completed through said spring and contact member is insured from a comparatively small elongation of the wire.

'7. A thermostatic switch'comprising a metallic sheath, a metal spring having one of its ends secured to said sheath and the other' end normally positioned in axial alignment therewith, a wire adapted to expand rapidly under the action of heat and having a high coefficient of expansion, one end of the said wire being connected to the free end of said spring and the other to a tensioning device carried by said sheath, a contact member carried by said sheath but electrically insulated therefrom, the design of said spring being such that a slight release of the tension on the wire is translated to the spring in a greatly amplified form, whereby a positive rupture of a circuit completed through said spring and contact member is insured from a comparatively small elongation of the wire.

8. A thermostatic switch comprising a periorated casing, a wire stretched longitudinally of said casing, the apertures in said casing being disposed in sets mutually opposed in respect to said wire so as to create cross currents, and the respective sizesof said apertures being in a determined relationship so that a concentration oi heat waves is effected within the casingwhen mounted horizontally in respect to its longitudinal axis.

9. A thermostatic switch comprising two thermostatic members having heat capacities substantially different, means to concentrate heat waves upon the thermostatic member; which is characterized by its lower heat capacity, and an electric contact operated by the relative expension of said member.

GEORGES HENRI LOUIS GASTON BORY. 

